Closed Loop Stimulation

Has anyone got any feedback / advice on the effectiveness  'Closed Loop Stimulation'  - Biotronik's rate response algorithm? 

Thank you for any replies.



by Persephone - 2023-01-20 12:57:35

Hi Penguin - the Biotronik CLS works for me - age 60, moderately active - can't comment on intense exercise or specific sports. 100% V-paced, 15% A-paced.

Biotronik CLS

by ourswimmer - 2023-01-20 13:16:18

I have uncomplicated sinus node dysfunction with chronotropic incompetence but no heart block or tachycardia. Last interrogation said 90+% atrial pacing but only 1% ventricular pacing. My Biotronik device works great for me. I believe the CLS response is set to "moderate" sensitivity but I don't know what the other parameters are. It raises my HR to meet demand when I swim, walk, and lift weights, and doesn't raise it unnecessarily every time I get up from my chair.

Thank you both !

by Penguin - 2023-01-20 13:34:38

Persephone & Our Swimmer,

Thank you for replying - kind of you!

I've read reports of CLS being very sensitive and raising the Heart rate inappropriately. Do you find this?  Comments on another thread have suggested it can be tricky to get the programming right.  Is that a reference to CLS do you think or other settings? 

I honestly know nothing at all about Biotronik, so any advice / guidance would help. 

Also re: v.pacing. Our Swimmer - With it being a DDD device how do you find any algorithms for limiting unnecessary v.pacing? 

Would be grateful to hear. 

"know nothing at all about Biotronik"

by Persephone - 2023-01-20 19:56:24

In my opinion, that's OK, so long as your clinic knows about them. My clinic kind of acted like a newbie (not sure what the dynamics were) but has since been more proactive with working in tandem with a Biotronik rep on the regular.

It took me a few weeks to fully adjust to the CLS being turned on, which was about 1 year post implant. Then things settled down and I felt great. I have not had the "too much too soon" kind of feeling others report - the adjustment resulted in an overall higher resting heart rate but once I got used to that, all has been well. Best wishes to you.


v. pacing

by ourswimmer - 2023-01-20 22:32:11

I don't know the answer to your question about "limiting unnecessary v.pacing." As far as I know, I have no conduction abnormalities. My SA node in its unmodified state has just become indifferent to "go faster" signals. (Like Bartelby, the Scrivener, it simply "would prefer not to.") But once my device juices the SA node, the electrical signal propagates through the rest of my heart as it should. I should never need any ventricular pacing and indeed apparently I don't.

I am definitely fortunate, but I really have never given the device programming any thought. I needed it; I explained to my cardiologist and electrophysiologist what activities and activity level I valued; they and the surgeon and the device rep made it work. All I know now is that I never notice the device doing its pacing thing. When I need more BPM I get them, and I don't ever feel as if I have more BPM than I need.

Do you find that your heart rate leaps around with stress

by Persephone - 2023-01-21 12:27:22

No. I think I understand where you're coming from based on Biotronik's literature. I could be the poster child for intense anxiety, and again - no, CLS has not had a negative effect. In fact, it helps immensely because I have less fear about being able to do the things I want to do.

My case was I guess one of the odder ones in that I "failed" my stress test, they only got maybe 90 seconds of data on me, and out I went on a stretcher to the ER for the PM implant. Proper planning would have been better, but it was what it was. The diagnosis I got from those seconds was CHB which "normally" wouldn't need atrial pacing but turns out I do need it.


by Penguin - 2023-01-21 17:48:31

Thank you Persephone, that's really interesting.  I found the research I've read on CLS and how it picks up on emotion and raises heart rate fascinating.  

That stress test sounds well .... stressful!  I'm pleased the pacemaker ultimately worked out so well for you. 

Thank you so much for your feedback. It's really good of you to share.

Biotronik CLS

by Granted - 2023-01-27 17:40:52

My Biotronik PM was implanted 7 weeks ago.  As soon as I left the hospital I experienced racing heartrate runs just sitting, turning over in bed, leaning down to tie a shoe, reaching up to remove something from a shelf etc.  Called my EP and cardiologist multiple times, had multiple in office visits explaining my experience and one ER visit.  Even wore a Holter monitor for 48 hours.  Was told over and over again "the PM is working perfectly" you need a beta blocker, well now you must need more beta blocker, well you are probably depressed and stressed etc). Finally, the cardiologist told me I was probably being "overpaced" and told me to have the EP reprogram the PM.  The EP and PM tech would not listen to me and kept saying the cardiologist was wrong I wasn't being overpaced.  I had the audacity to ask the ER and PM tech to explain my PM programming to me, and no joke, it's 2023, but both the EP and PM tech each said its very complicated, you wouldn't understand and I don't have time to explain it because I have other patients waiting).  Before I could compose myself and respond to them myself my husband yelled at them and said this is crazy and what she is experiencing is not normal. As soon as my husband yelled at him, the EP says, well, we could turn off the CLS. I did not know what the CLS was in that moment and I am still not sure what the CLS is today, but my heart hasn't raced at all since it was turned off, I stopped the beta blocker,  and I feel like I have my life back. And, thank goodness,  I have an appointment with a new EP at a major teaching hospital next week!  

That sounds awful

by Penguin - 2023-01-28 06:38:20

Hi Granted,

Many thanks for your response. I've been reading through old posts on this forum re: CLS and there are some mixed responses. Your experience doesn't sound good. There's nothing worse than being told that something you're experiencing can't be happening when it clearly is. I'm with you on that one! 

Turning off the CLS sounds like the right option to stop your symptoms, but what will you do about rate responsive pacing without it?  Do you have chronotropic incompetence?  If so you will probably need to have it switched back on. 

I hope that the major teaching hospital will be able to sort this out for you. Would you let me know how you get on if you have time? I'd be very interested.

Best Wishes


Biotronik CLS

by Granted - 2023-02-18 02:24:14


My appointment with the new EP was a huge relief. I felt they listened to my concerns and responded appropriately.  They agreed the CLS should be off and they adjusted my lower and upper rates. They are monitoring my PM now and I have not had any issues with racing HR since the CLS was turned off.  I am back to my full exercise schedule every week (tennis, walks, yoga and strength training) and feel that my PM is in sync  with my exercise efforts. I don't have chronotropic incompetence, but before the CLS was turned off,  and I was on the beta blocker, I felt like my HR during exercise was suppressed by the PM and/or the beta blocker. 



by Penguin - 2023-02-20 03:32:05


Thanks for coming back on this. That's good news that turning off CLS did the trick for you and you're able to exercise again. 

I think - and check with your doctor - that beta blockers keep h/rates within limits so that may be what was going on. Re: the PM - apparently there are two rate response algorithms on a Biotronik device - the CLS and an accelerometer.  I've heard that CLS and the accelerometer don't need to be switched on together - it's an either / or scenario - and that on Biotronik devices RR only takes you up to 160 bpm.  (These nuggets are based on advice from members on here who have Biotronik devices or who have knowledge of them.)  As always, any advice / comments are best checked with your EP / pacing clinic. 

Best Wishes

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